Technical Field
The present disclosure generally relates to rotating electrical machines, such as generators or electric motors, and more particularly to rotating electrical machines employed in environments in which low weight and/or a configurable structure may be advantageous.
Description of the Related Art
Rotating electrical machines may take a various forms, the most ubiquitous being generators and electric motors. Rotating electrical machines typically include two major components, denominated as the stator and the rotor. The stator typically remains stationary, although in some implementations may move. The rotor is typically mounted for rotation with respect to the stator. Rotating electrical machines conventionally employ wire windings and magnets. In the case of generators, relative movement of the magnets, typically permanent magnets, with respect to the wire windings induces an electrical current in the windings. In the case of electric motors, passage of electrical current through various windings produces electromagnetic forces, which attract, and optionally, repel the magnets, inducing rotation. The wire windings may be carried by the stator, while the magnets may be carried by the rotor to rotate therewith. Conversely, the magnets may be carried by the stator, while the wire windings may be carried by the rotor to rotate therewith. One of skill in the art will recognize that a wide variety of arrangements are possible, including arrangements other than those described above.
Rotating electrical machines are used in a large variety of different environments for various applications. Many of these environments and/or applications impose certain constraints on the design and/or operation of the rotating electrical machines. For example, rotating electric machines may be employed in turbines, for instance for use in generating electric power from renewable resources such as wind or water. In the case of wind powered turbines, the rotating electric machine is typically installed in a nacelle or other housing at the top of a relatively tall tower. Such places significant constraints on the size (e.g., diameter) and/or weight of the rotating electric machine. Given the expense of replacing malfunctioning rotating electric machines in such environments, such also requires a design that is robust and able to operate over long periods of time with minimal or no replacement or repair. Even when employed in more accessible environments, for instance as an electric motor in a vehicle such as a hybrid or electric automobile, truck or bus, constraints exist on size and/or weight, and robustness is always desirable.
An electric machine may employ a distributed bearing, for example spaced radially outwardly of a longitudinal center of a rotor and stator assembly. The distributed bearing may take the form of a wire race bearing, which positions a rotor assembly relative to a stator assembly to maintain an air gap therebetween. The rotor assembly may be concentrically located within the stator assembly. Electrically insulative fasteners may couple a race assembly to the stator or rotor assembly. Compensation fastener assemblies may couple the wire race assembly to the rotor or stator assembly, to compensate for differential expansion (for instance, thermal differential expansion along a longitudinal axis of the electric machine). A number of electric machines may be arranged in series, for example with drive shafts arranged along a common axis, and may be coupled to be driven by the same source of motion (e.g., propeller of a wind turbine, without or with a gear box).